Project Summary/Abstract Severe problem behavior (SPB; e.g., aggression, elopement, and self-injury) engaged in by individuals with intellectual and developmental disability is a major public health concern. These behaviors can be so severe that even a single instance of SPB may result in injury to self or others. One promising treatment strategy involves identifying behavioral indicators that an episode of SPB is imminent and interrupting the escalating sequence of behavior before SPB occurs. These behavioral indicators are called precursors to SPB, and are not as severe or dangerous as SPB. Given that SPB may cause harm to self or others, identifying precursors to SPB is particularly important; however existing research on precursors has been opportunistic, resulting in a loose collection of clinical case reports. The proposed research will examine methods to identify and better understand precursors. Specifically, this research will assess the likelihood of precursors to SPB (Studies 1 and 2) and refine existing methodologies of precursor identification to better understand the specific relation between precursors and SPB (Study 3). This research will be conducted within a sample of 80 individuals who are at the most risk for injury due to the severity of their SPB. In Study 1, we will examine the context in which SPB is occurring using second-by-second data analysis to identify likely precursors through a probability analysis. In Study 2, we will examining how precursors and SPB change across two experimental conditions to determine whether the precursor and SPB are occurring for the same reason. In Study 3, we will determine the relation between the precursor and SPB by preventing the occurrence of the precursor and examining the effect on SPB. In addition, although not the primary focus of this study, secondary analyses will be conducted on behavior-specific and participant specific variables where precursors are and are not found. Finally, although a precursor-treatment study is premature at this time, we will collect pilot data on precursor-based treatments to inform future research. We anticipate that we will able to identify a precursor and determine the precursor-SPB relation in a high proportion of individuals who engage in SPB. Findings could both inform practice, and promote research investigating precursor-based treatments that that could prevent occurrences of SPB, and thus help limit the risks associated with these behaviors.